Tidal influence on Fish Faunal Distribution and Species Diversity in Kakum Estuary, Ghana

Abstract

Estuarine and coastal areas are complex and dynamic aquatic environments. In such an area, where river water mixes with seawater, a large number of physical and chemical processes take place, which may influence water quality thereby affecting the distribution and diversity of the biota. The study was conducted in the transition period of dry and wet conditions from February to May 2018. The influence of low and high tides on the hydrographic parameters such as salinity, dissolved oxygen, and water temperature in the three sampling stations was analyzed in relation to fish faunal distribution and species diversity of the estuary. The common fish species in the estuary were juveniles of Sarotherodon melanotheron and Mugil cephalus, Liza falcipinnis and the crab Callinectes amnicola. These species were encountered during both low and high tides in all sampling stations, which indicates their adaptation to a broader range of hydrographic conditions. The majority of species encountered were juveniles. Although most of the fish species were marine in origin, some including Tilapia zillii, Hemichromis fasciatus and Apolochelichthys spilauchen were freshwater in origin whilst, S. melanotheron is a resident fish species in the estuary. Length-frequency distribution and length-weight relationships of S. melanotheron, T. zillii, L. falcipinnis, Mugil cephalus, and Eucinosthomus melanopterus which were the five most dominant fish species during the period of study in Kakum estuary were analyzed. The modal sizes of the dominant fish species were mainly juveniles in the length-frequency distribution. The length-weight relationships of S. melanotheron, L. falcipinnis and M. cephalus showed allometric growth, whereas that of T. zillii and E. melanopterus showed isometric growth. The study, therefore, identified that Kakum estuary is a transitional zone for both marine and freshwater fish species using the estuarine ecosystem as nursery grounds. The presence of marine and freshwater-origin species, and resident species in the estuary further suggest that estuaries are highly dynamic, and slight changes in their environment can cause a great deal of harm to its fish biota.